1. Field of the Invention
This invention relates to a control valve assembly and more particularly to an isolation valve that requires a two-way seal.
2. Discussion of the Art
One common use of an isolation valve is to provide a pneumatic backup in the event of an electronics failure associated with an electronic braking system (EBS). The isolation valve includes first and second seal assemblies on a movable piston that alternately and selectively isolate supply pressure to an outlet or delivery port from either a traditional pneumatic braking system or the electronic braking system. Typically, the two supply ports that communicate with a valve chamber are axially spaced apart. Consequently, movement of the piston between first and second positions alternately isolates one of the supplies from the delivery port.
An insert and bonded rubber sealing element is commonly used on the piston to engage the valve seat associated with the first and second positions of the piston. That is, opposite faces of the insert have an elastomer or rubber material integrally bonded thereon. Although an effective seal is provided, the insert and bonded rubber sealing element is a relatively expensive item. Thus, a need exists for a suitable substitute that provides effective isolation, i.e., two-way seals, at a significantly reduced manufacturing cost.